Group of objects appear blurry and distorted after render?
First of all, the ID Mask doesn't return a part of the image, but rather a greyscale value that is meant to be used to mask parts of the original image, e.g. by use of a Set Alpha node or an Alpha Over node. The following node setup is a template for adding glow and blur to parts of an image. It can be adapted to more specific needs, but in your case I think it'll work well as it is (click to enlarge).



The first Mix node mixes the original image with black, making it black where the mask is black and the original colour where the mask is white, and a blend of the two where, if at all, the mask has any shades of grey.

I changed the Glare node. I set the quality to High. Then I set the Mix to 1.000. This makes the node output the processed image only. 0.000 means a 50/50 mix between the original and the processed images, and -1.000 means original image only. By turning the Threshold down to 0.000 all pixels are affected. Higher values makes pixels with intensity below the threshold pass through unaffected. Note that the effect of the Glare node will be less visible if you render a larger image.

I also changed the Blur node. I set it to Gaussian rather than Fast Gaussian, and increased the amount slightly and turned the Size up to 1.000.

I also did turn down the emission strength in the material for the bars to 1.000. That, however, is just personal taste.

And this is the result I got (click to enlarge, the reason the background is pink, is that I don't have the image you used to texture it).